avoid use of all ctype macros

* cfg.mk (disable_temporarily): Don't disable sc_avoid_ctype_macros.
* fish/tilde.c: Remove unnecessary inclusion of ctype.h.
* bootstrap: Add gnulib's c-ctype module to the list.
* daemon/m4/gnulib-cache.m4: Likewise.
* daemon/ext2.c: Include "c-ctype.h", not <ctype.h>.
Use c_isspace, etc, rather than isspace.
* daemon/guestfsd.c: Likewise.
* daemon/lvm.c: Likewise.
* daemon/proto.c: Likewise.
* fish/fish.c: Likewise.
* fish/tilde.c: Likewise.
* src/generator.ml: Likewise.
* src/guestfs.c: Likewise.
* examples/to-xml.c: Likewise.
* examples/Makefile.am (to_xml_CPPFLAGS): Add -I$(top_srcdir)/gnulib/lib
so inclusion of "c-ctype.h" works.
(to_xml_CPPFLAGS): Rename from to_xml_CFLAGS.